Physics · Science General

Acoustics and Sound Waves

2,160 Questions

Acoustics and sound waves deal with mechanical vibrations traveling through media like air and water. Key concepts include wave reflection, beats, echoes, the Mach number, and infrasound. These physics fundamentals are regularly tested in general science sections of multiple competitive exams.

Sound wave propagationEchoes and reflectionWave interferenceMach numberInfrasound frequency

Acoustics and Sound Waves Questions

Multiple choice physics free, damped and forced oscillations resonance: examples and uses resonance oscillatory motion

A student is performing the experiment of resonance Column. The diameter of the column tube is $4\ cm$. The frequency of the tuning fork is $512\ Hz$. The air temperature $38^{o}C$ in which the speed sound is $336\ m/s$. The zero of the meter scale coincides with the top end of the Resonance Column tube. When the first resonance occurs, the reading of the water level in the column is:

  1. $14.0\ cm$
  2. $15.2\ cm$
  3. $16.4\ cm$
  4. $17.6\ cm$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For $I^{st}$ resonance

$l _1 + e = \dfrac{\lambda}{4}$ or $l _1 = \dfrac{\nu}{4f} - 0.3d = 15.2\space cm$

Multiple choice physics free, damped and forced oscillations resonance: examples and uses resonance oscillatory motion

If two vibrating systems are in resonance, then :

  1. Their amplitudes are equal

  2. Their frequencies are equal

  3. Their temperatures are equal

  4. Their intensities are equal
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Answer is C.

Resonance is a phenomenon that consists of a given system being driven by another vibrating system or by external forces to oscillate with greater amplitude at some preferential frequencies. Frequencies at which the response amplitude is a relative maximum are known as the system's resonant frequencies, or resonance frequencies. 
When both the bodies vibrate, they will start to vibrate with the same frequency.

Multiple choice physics free, damped and forced oscillations resonance: examples and uses resonance oscillatory motion

Resonance is exhibited in 

  1. quartz crystals

  2. clocks

  3. ear membranes

  4. pendulum
Reveal answer Fill a bubble to check yourself
A,B,C,D Correct answer
Explanation

$Answer:-$ A,B,C,D

Various examples of mechanical resonance include:

  • Most clocks keep time by mechanical resonance in a balance wheel,pendulum, or quartz crystal.
  • Orbital resonance as in some moons of the solar system's gas giants.
  • The resonance of the basilar membrane in the ear.
  • Making a child's swing swing higher by pushing it at each swing.
  • A wineglass breaking when someone sings a loud note at exactly the right pitch.

Multiple choice physics free, damped and forced oscillations resonance: examples and uses resonance oscillatory motion

What conditions are necessary to produce resonance in an object?

  1. The object must have at least one natural frequency of vibration.

  2. The object must be driven by an external vibrating force.

  3. The frequency of the external vibrating force must match the object's natural frequency of vibration.

  4. All of the above.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Resonance is a phenomenon in which the periodic oscillatory force acting on an object has a frequency of vibration same as the natural frequency of the object. In this, the object vibrates with a large amplitude.

Multiple choice physics free, damped and forced oscillations resonance: examples and uses resonance oscillatory motion

Resonance occurs when a vibrating system or external force drives another system to ____ with greater _ at a specific preferential ______. Fill in the blanks. 

  1. oscillate, amplitude, frequency

  2. oscillate, frequency, amplitude

  3. vibrate, velocity, frequency

  4. vibrate, frequency, velocity
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$Answer:-$ A

In physics, resonance is a phenomenon that occurs when a given system is driven by another vibrating system or external force to oscillate with greater amplitude at a specific preferential frequency.

Resonance occurs when a system is able to store and easily transfer energy between two or more different storage modes (such as kinetic energy and potential energy in the case of a pendulum). However, there are some losses from cycle to cycle, called damping. When damping is small, the resonant frequency is approximately equal to the natural frequencyof the system, which is a frequency of unforced vibrations. Some systems have multiple, distinct, resonant frequencies.
Resonance phenomena occur with all types of vibrations or waves: there is mechanical resonance, acoustic resonance, electromagnetic resonance, nuclear magnetic resonance(NMR), electron spin resonance (ESR) and resonance of quantum wave functions. Resonant systems can be used to generate vibrations of a specific frequency (e.g., musical instruments), or pick out specific frequencies from a complex vibration containing many frequencies (e.g., filters).

Multiple choice physics free, damped and forced oscillations resonance: examples and uses resonance oscillatory motion

In a resonance tube with tuning fork of frequency $512 \ Hz$, first resonance occurs at water level equal to $30.3 \ cm$ and second resonance occurs at $63.7 \ cm$. The maximum possible error in the speed of sound is

  1. $51.2 \ cm/s$
  2. $102.4 \ cm/s$
  3. $204.8 \ cm/s$
  4. $153.6 \ cm/s$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$\begin{array}{l} { l _{ 1 } }+e=\frac { V }{ { 4f } } \to \left( i \right)  \ { l _{ 2 } }+e=\frac { { 3V } }{ { 4f } } \to \left( { ii } \right)  \ Sub\, \, \left( { ii } \right) \, \, & \, \, \left( i \right)  \ { l _{ 2 } }-{ l _{ 1 } }=\frac { { 2V } }{ { 4f } }  \ { l _{ 2 } }-{ l _{ 1 } }=\frac { V }{ { 2f } }  \ \frac { { \Delta \left( { { l _{ 2 } }-{ l _{ 1 } } } \right)  } }{ { { l _{ 2 } }-{ l _{ 1 } } } } =\frac { { \Delta V } }{ V }  \ \Delta V=2f\Delta \left( { { l _{ 2 } }-{ l _{ 1 } } } \right) =2f\left( { \Delta { l _{ 1 } }+\Delta { l _{ 2 } } } \right) ......for\, \, man\, \, error \ =2\times 512\times \left( { 0.1+0.1 } \right) =204.8\, \, cm/s \end{array}$

Multiple choice physics free, damped and forced oscillations resonance: examples and uses resonance oscillatory motion

The third overtone of a pipe is found to be in unison with the first overtone of an open pipe. The ratio of lengths of the pipes is 

  1. $\dfrac { 3 }{ 4 }$
  2. $\dfrac { 3 }{ 5 }$
  3. $\dfrac { 2 }{ 5 }$
  4. $\dfrac { 7 }{ 4 }$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Third overtone of a closed pipe is 7v/4L1. First overtone of an open pipe is 2v/2L2 = v/L2. Equating: 7/4L1 = 1/L2. Thus L1/L2 = 7/4.

Multiple choice physics free, damped and forced oscillations resonance: examples and uses resonance oscillatory motion

In Resonance tube experiment, if $400\ Hz$ tuning fork is used, the first resonance occurs when length of air column in the tube is $19\ cm$. If the $400\ Hz$. tuning fork is replaced by $1600\ Hz$ tuning fork then to get resonance, the water level in the tube should be further lowered by (take end correction $= 1\ cm)$.

  1. $5\ cm$
  2. $10\ cm$
  3. $25\ cm$
  4. $20\ cm$
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice physics free, damped and forced oscillations resonance: examples and uses resonance oscillatory motion

The first resonance length of a resonance tube is 40 cm and the second resonance length is 122 cm.third resonance length of the tube will be

  1. 200 cm

  2. 202 cm

  3. 203 cm

  4. 204 cm
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The first resonant is$:-$

${L _1} = \frac{\lambda }{4}$
The second resonant length is$:-$
${L _2} = \frac{{3\lambda }}{4}$
the third resonant length of resonance tube is$:-$
${L _5} = 5\,\,\frac{\lambda }{4} = \frac{5}{3}\,\,{L _3} = \frac{5}{3}\left( {122\,cm} \right)$
Hence,
option $(C)$ is correct answer.

Multiple choice physics free, damped and forced oscillations resonance: examples and uses resonance oscillatory motion

A organ pipe open on both ends in the $n^{th}$ harmonic is in resonance with a source of $1000 \,Hz$. The length of pipe is $16.6 \,cm$ and speed of sound in air is $332 \,m/sec$. Find the value of $n$.

  1. $1$
  2. $2$
  3. $3$
  4. $4$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$f = \dfrac{nV}{2\ell}$

$1000 = \dfrac{n \times 332}{2 \times 16.6 \times 10^{-2}}$

$10 = \dfrac{n \times 332}{33.2}$

$n = 1$

Multiple choice physics free, damped and forced oscillations resonance: examples and uses resonance oscillatory motion

A vibrating object will pick out its __________ from a complex excitation and vibrate at those frequencies.

  1. resonant frequency

  2. natural frequency

  3. both

  4. none
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A vibrating object will pick out its resonant frequencies from a complex excitation and vibrate at those frequencies, essentially "filtering out" other frequencies present in the excitation.

Multiple choice physics free, damped and forced oscillations resonance: examples and uses resonance oscillatory motion

Which one does not work on principles of resonance?

  1. T.V

  2. Radio

  3. Microwave oven

  4. Bulb
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Resonance in an electrical circuit is a phenomenon in which the inductive reactance and the capacitive reactance become equal and cancel each other.

As a result, the impedance of the circuit becomes the least and maximum current flows through the circuit. This happens only at a particular frequency of the AC power supply, known as resonant frequency. 
All the devices except bulb work on this principle. The circuit in them is tuned in order to make their resonant frequency matching with the desired one. This is done by adjusting the values of the inductor or the capacitor.
In a bulb, there is only pure resistance and no reactive component. There is no question of resonance.